The overall objectives of this project are to study loci that map in the major histocompatibility regions of man and mouse. We have proposed to study the genetic determinants of glyoxalase-I (GLO), of various complement components and of PGM-3 and to establish which of these maintain homology in the two species. We have mapped the loci for GLO and C3 in mice with respect to H-2. The order (from the centromere) is: GLO (1.7) H-2.K (0.5) H-2-D (11.5) C3 (the numbers are the recombination fractions). This order was ascertained in crosses informative for GLO, H-2 and C3, in experiments involving more than 800 offspring. We have tested the association of H-2.7 with C4 (the Ss locus) and found that: 1) serum from H-2.7 (plus) animals will invariably block the hemagglutinating ability of anti-H-2.7 on adequate targets, and 2) anti-Ss reagents raised with pooled Ssh sera contains specific anti-H-2.7. Other groups have also shown (and already published) similar evidences, demonstrating the homology between Chido, Rodgers and H-2.7. A "new" genetic variation has been uncovered in these studies and will be explored: it is a quantitative variant of GLO. Three alleles have already been identified. No case of complete deficiency of hemolytic complement has been uncovered in testing over 25,000 samples from humans.